Project description:Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the brain. Among characteristics of MS pathology are cortical grey matter abnormalities, which have been linked to clinical signs such as cognitive impairment. To understand MS cortical grey matter lesion pathogenesis, we performed differential gene expression analysis of MS cortical normal-appearing grey matter (NAGM) and grey matter lesions. HLA-DRB1 is the transcript with highest expression in MS NAGM with a bimodal distribution among the examined cases. Genotyping revealed that every case with the MS-associated HLA-DR15 haplotype also shows high HLA-DRB1 expression. Quantitative immunohistochemical analysis confirmed the higher expression of HLA-DRB1 in HLA-DRB1*15:01 cases at the protein level. Analysis of grey matter lesion size revealed a significant increase of cortical lesion size in cases with high HLA-DRB1 expression. Our data indicate that increased HLA-DRB1 expression in the brain of MS patients may be an important factor in how the HLA-DR15 haplotype contributes to MS risk in the target organ.
Project description:Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the brain. Among characteristics of MS pathology are cortical grey matter abnormalities, which have been linked to clinical signs such as cognitive impairment. To understand MS cortical grey matter pathogenesis, we performed differential gene expression analysis of MS normal appearing grey matter (NAGM) and control grey matter. HLA-DRB1 is the transcript with highest expression in MS NAGM with a bimodal distribution among the examined cases. Genotyping revealed that every case with the MS-associated HLA-DR15 haplotype also shows high HLA-DRB1 expression. Quantitative immunohistochemical analysis confirmed the higher expression of HLA-DRB1 in HLA-DRB1*15:01 cases at the protein level. Analysis of grey matter lesion size revealed a significant increase of cortical lesion size in cases with high HLA-DRB1 expression. Our data indicate that increased HLA-DRB1 expression in the brain of MS patients may be an important factor in how the HLA-DR15 haplotype contributes to MS risk in the target organ.
Project description:Using laser capture microscopy, white (WM) and grey matter (GM) demyelinated areas and normal appearing matter was collected from histologically verified leukocortical lesions from snap-frozen human post mortem tissuederived from Multiple Sclerosis patients. Our data shows large differences in gene expression in WM and GM demyelinated areas (compared to their respective normal appearing matter) even when the demyelinated areas are spatially connected such as in leukocortical lesions. Thus, we show that WM demyelinated areas and GM demyelinated areas are distinct entities with distinct pathology. Therefore findings observed in WM demyelinated areas cannot be generalized to GM demyelinated areas.
Project description:Focal white matter lesions occur in most neurodegenerative disorders. Despite occurring early in disease, white matter lesions are considered either independent of, or secondary to, grey matter neuroinflammation, synapse loss and altered neuronal activity. Notably their functional impact on neuronal circuits has been understudied. To address this, we generated a focal white matter lesion in an anatomically well-defined circuit, in which white matter lesions occur in many neurodegenerative disorders. Here we show that focal white matter lesions evoke transient neuronal activity changes and microgliosis, with subsequent synapse loss and increased microglia engulfment in the grey matter, which is reversed if myelin regeneration completes. Grey matter microgliosis is often considered detrimental but we show that it is an integral part of the myelin regenerative process. When we prevent these transient changes in the grey matter, myelin regeneration is blocked in the white matter. Conversely, inducing myelin regeneration failure leads to chronic neuroinflammation in the grey matter, suggesting that myelin regeneration failure drives sustained grey matter microglial activation. This recapitulates the low-grade inflammation considered to be a dominant mechanism underlying neurodegeneration. Our findings reveal a form of regenerative plasticity coupling white matter integrity to grey matter function - a novel mechanism of neuroplasticity that may underlie multiple neurodegenerative conditions - and highlights the potential of targeting myelin regeneration to prevent chronic inflammation.
Project description:Focal white matter lesions occur in most neurodegenerative disorders1-4. They are well characterised in multiple sclerosis (MS) but much less understood in other conditions. Despite occurring early in disease, white matter lesions are considered either independent of or secondary to grey matter neuroinflammation, synaptic loss and altered neuronal activity5-8. Notably their functional impact on neuronal circuits has been overlooked. To address this, we performed a focal white matter lesion in an anatomically well-defined circuit, in which white matter lesions occur in many neurodegenerative disorders. Here we show that focal white matter lesions evoke transient neuronal activity changes and microgliosis, synaptic loss and increased engulfment in the grey matter, which resolves by the time myelin regeneration completes. Synaptic loss and microgliosis are often considered detrimental but we show they are instead an integral part of the myelin regenerative process. When we prevent these transient changes in the grey matter, myelin regeneration is blocked in the white matter. Conversely, inducing myelin regeneration failure leads to chronic neuroinflammation in the grey matter, suggesting that myelin regeneration failure drives sustained microglial activation. This recapitulates the low-grade inflammation considered to be a dominant mechanism underlying neurodegeneration8-11. Hence, we present a novel mechanism that may underlie multiple conditions and highlight the potential of targeting myelin regeneration to prevent chronic neuroinflammation.
Project description:Microglia are brain-resident, myelin-phagocytosing cells, yet their role in lesion initiation in grey and white matter regions in multiple sclerosis (MS) is unclear. We isolated primary microglia from both, occipital cortex and corpus callosum, of 10 MS and 11 control donors and studied their transcriptional profile by RNA sequencing, thereby identifying regional and MS-associated changes. Identification of pathways underlying regional differences showed a relatively increased type I interferon response in cortical grey matter microglia, while white matter microglia more highly expressed NF-κB pathway genes. In normal-appearing white matter MS tissue, lipid metabolism genes were increased, suggesting processing of myelin by microglia already in areas seemingly devoid of MS pathology. Normal-appearing grey matter MS microglia showed increased activation of glycolysis and metal ion homeostasis, possibly reflecting microglia reacting to iron depositions. Notably, expression of genes associated with microglia homeostasis were hardly changed, suggesting that subtle regional changes in MS-associated microglia do not yet affect their resting state.
Project description:Multiple Sclerosis (MS) is a chronic inflammatory and demyelinating disease of the central nervous system (CNS), where ongoing demyelination and remyelination failure are the major factors for progressive neurological disability. In this report, we employed a comprehensive proteomic approach and immunohistochemical (IHC) validation to gaininsight into the pathobiological mechanisms that may be associated with the progressive phase of MS disease. Isolated proteins from myelinated regions, demyelinated white matter lesions (WMLs), and grey-matter lesions (GMLs) of well-characterized progressive MS brain tissues were subjected to label-free quantitative mass spectrometry (LFQ-MS). Using a system-biology approach, we detected increased expression of proteins belonging to mitochondrial electron transport complexes and oxidative phosphorylatio pathway in WMLs. Intriguingly, many of these proteins and pathways had opposite expression patterns in GMLs of progressive MS brains. A comparison to the huma MitoCarta database mapped the mitochondrial proteins to mitochondrial subunits in both WMLs and GMLs. Taken together, we provide evidence of opposite expression of mitochondrial proteins in response to demyelination of white- and grey-matter regions in progressive MS brain.